One of the most difficult procedures in the manufacture of knitted T-shirts has been the attachment of tubular sleeve sections to knitted shirt bodies. In a typical manufacturing procedure for the production of knitted T-shirts, it is customary for shirt bodies and sleeve sections to be separately produced and brought together at a so-called sleeve insertion operation, at which the individual sleeve sections are sewn to the shirt body. The shirt bodies are formed with sleeve openings at opposite sides, and the sleeve sections, previously hemmed at their outer ends, are joined at their raw inner ends to the sleeve openings of the shirt body.
Manual sewing of the sleeve sections to the shirt body is labor-intensive and adds considerable cost to the production of the shirt. Accordingly, significant effort has been made to automate the sleeve insertion procedure, with the objective of enabling it to be performed reliably, with a satisfactory quality level, and at a sufficiently high speed to justify the capital expense of the required equipment.
One of the early efforts to automate the sleeve attachment procedure is reflected in the Ernst Schramayr et al. U.S. Pat. No. 5,329,919, assigned to Jet Sew Technologies, Inc., Barneveld, N.Y. In that patented system, a shirt body is placed over a cylindrical body form, which presents the sleeve openings at opposite ends of the form, with the shirt body oriented right-side-out. Sleeve sections are then applied, with an inside-out orientation, hem end first, over the cylindrical body form. Procedures are followed during the application steps to align the raw edges of each shoulder opening and each associated sleeve in a predetermined plane. In a subsequent operation, the two parts are sewn together by operating a sewing head in a circular path about the aligned edges of the sleeve sections and sleeve openings.
Although the system of the '919 patent is an improvement over procedures previously available, a problem has been observed. This problem arose from the necessity of applying the pre-hemmed sleeve section externally over the shirt body supported on a cylindrical form. In some cases, this results in overstretching of the sleeve section, particularly since, in many cases, the hemmed edge of the sleeve section is of smaller diameter than the raw edge to be joined with the sleeve opening.
The problem that is observed in the system of the above mentioned U.S. Pat. No. 5,349,919 is addressed in a subsequent development, which forms the subject matter of copending application Ser. No. 08/294,095, filed Aug. 22, 1994. In the system of the copending application, provision is made for loading of the sleeve sections onto tapered sleeve cones which are then positioned on the inside of a body form, rather than over the outside as in the system of the '919 patent. A shirt body is then loaded over the body form, and the aligned edges of the sleeve sections and shirt bodies are sewed by a circular movement of the body form relative to a sewing head.
While in the patented apparatus, the sewing head itself is caused to traverse through a circular path for sewing the shoulder seam, in the apparatus of the pending application, the loaded body form preferably is detached from its loading position and the body form itself is caused to rotate relative to a fixed sewing head.
The system of the pending application represents an improvement over the patented apparatus in that the sleeve sections are exposed to less stretching. They are nevertheless still exposed to some degree of stretching in order to load them onto the conical sleeve cones. In addition, and possibly more importantly, the various body and sleeve forms utilized in the operation are size specific. Accordingly, a plurality of sets of forms are required for the manufacture of a full range of shirt sizes, which adds to the capital requirements of the system.
The method and apparatus of the present invention address and eliminate the problems observed in the earlier systems described above, enabling the sleeve insertion operation to be accomplished with a considerably reduced cycle time, and with much simpler, less costly equipment. In accordance with procedure of the invention, each sewing location is provided with a load fixture which receives and supports only a narrow marginal portion of the raw (shoulder) edge of a sleeve section, allowing the hemmed end of the sleeve section to hang free. The shoulder section of a shirt body is then loaded over the sleeve section, and a narrow margin of fabric adjacent the sleeve opening is supported in surrounding relation to the previously loaded sleeve section. Only the shoulder edge margin of the shirt body is engaged and supported. For each of the edge margins, there is provided an edge sensing element, and an active edge guide device which responds to signals from the edge sensing element and serves to independently align the respective fabric edges on a continuous basis.
After loading of the sleeve and body sections, a sewing head is activated, and the edge margins of the sleeve and body sections are advanced past the needle position of a stationary sewing head to enable the sewing operation to take place. As the sewing progresses, the edges of the sleeve section and shirt body are automatically and independently aligned, immediately in advance of sewing. Among other things, this allows the machine operator to load the sleeve section and shirt body onto the load fixture with relatively minimum regard for precise initial alignment.
In a preferred form of the invention, each sewing station comprises a pair of generally opposed load fixtures and sewing heads, and the operator first loads a sleeve section and shirt body at one side, and then loads a second sleeve section and the opposite side of the shirt body on a second load fixture. The sewing operations then proceed, either sequentially or simultaneously, depending on the configuration of the equipment. The equipment required is size independent, with each load fixture advantageously consisting of a series of support rollers, including at least one such roller that is movable to place both fabric sections under light circumferential tension. This serves to equalize the circumferences of the sleeve and the shirt body shoulder opening, and also to facilitate edge guidance during sewing. The result is a high quality, pleat-free seam. Desirably, the movable roller means are retracted to accommodate the initial loading of a sleeve section, and thereafter moved to a position to place the fabric under the desired light tension for sewing.
In a preferred form of the invention, the load fixtures are pivotable to a position at least partially facing the machine operator, in order to facilitate the loading operations. Thereafter, the load fixtures can be pivoted to positions aligned with respect to a common axis to better accommodate the subsequent sewing operations.
Pursuant to the invention, a relatively simple, yet highly efficient sleeve insertion installation may be provided by arranging two sets of equipment adjacent to each other and preferably arranged at an angle, so that a single operator may load one station and, while that station is performing the necessary sewing operations, the operator can load the adjacent second station. The procedures according to the invention enable greatly reduced cycle times, representing a major improvement over procedures heretofore known. At the same time, the equipment required is far simpler and less costly.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments of the invention and to the accompanying drawings.